London Bombings 050707

Four explosions ripped across central London on Thursday 7 July, just 20
hours after the euphoric celebration on the 6th of London's winning of
the 2012 Olympic bid. The following
notes are from a BBC report:

As the death toll in London's worst day of terror in decades rose higher
than 50 on Friday, a senior police officer promised "implacable resolve"
to bring to justice the bombers who had attacked subway trains and a
bus.

With an unspecified number of bodies still to be removed from one
vermin-infested subway tunnel, British leaders from royalty to leftists
evoked wartime images to urge resolve.

The bomb explosions Thursday tore through three subway trains and a red
double-decker bus - one of London's most familiar icons - at the height
of the morning rush hour.

Initial police estimates said 37 people had died, but the number of
confirmed deaths rose to 49 on Friday, and the police said the tally
would exceed 50.

Our specification for the formal analysis was for departure of the
Stouffer Z from expectation over the full 24 hour day. (We had used only
a 4-hour period for 9/11, and later analysis indicated this was much too
short a time.) The first explosion was at 8:51 am (07:51 UTC), and was
followed by others at 8:56, 9:17, and 9:47. (This early info has been
changed: the three train bombs all exploded at about 8:50; the bus
explosion was at 9:47.) The result for this standard
analysis does not show a clear deviation, with Z=0.347 and p=0.364. The
following figure shows the data. There are interesting internal trends,
but it is not clear they are correlated with the bombings.

We learned a great deal from contextual analyses of the data on 9/11,
especially of the variance measure across the eggs. The next figure
shows this analysis for London. A notable (but only marginally
significant) drop in the variance occurs shortly before the first
explosion, followed by a return to expected levels a few hours after.

To provide a sense of scale, the absolute value of the
accumulating variance deviation on 050707 is compared with the same
measure on 010911. The attacks in both cases occurred over a period of
one or two hours, and the two data sets are aligned at the beginning of
the attacks. The figure is of course only an "aesthetic" presentation,
but it is interesting that in both cases there is an apparent symmetry
of response, beginning some hours early and persisting after the main
focal events.

A week after the terrorist bombing,
Prime Minister Tony Blair and Britons nationwide prepared to mark the
one-week anniversary of the London bombings with two minutes' silence at
noon (1100GMT) and a defiant gathering in Trafalgar Square, says the AP.
People across the 25-nation European Union also were being asked to
observe the two minutes' silence, EU officials said.
Takeoffs and landings were to be kept to a minimum during the two-minute
period at Heathrow and Gatwick airports, and no trains were to leave
London's main stations during the remembrance, officials said.

This memorial moment is very similar in concept and execution to one
held for the 9/11 attacks,
and it is instructive to compare the EGG
network response in the two cases. Both show a very steady decline of
the cumulative deviation in the period following the memorial silence.
This is not a formal analysis, but the parallel is striking.